Abstract

Cavitation often occurs in therapeutic applications of medical ultrasound such as shock-wave lithotripsy (SWL) and high-intensity focused ultrasound (HIFU). Because cavitation bubbles can affect an intended treatment, it is important to understand the dynamics of bubbles in this context. The relevant context includes very high acoustic pressures and frequencies as well as elevated temperatures. Relative to much of the prior research on cavitation and bubble dynamics, such conditions are unique. To address the relevant physics, a reduced-order model of a single, spherical bubble is proposed that incorporates phase change at the liquid-gas interface as well as heat and mass transport in both phases. Based on the energy lost during the inertial collapse and rebound of a millimeter-sized bubble, experimental observations were used to tune and test model predictions. In addition, benchmarks from the published literature were used to assess various aspects of model performance. Benchmark comparisons demonstrate that the model captures the basic physics of phase change and diffusive transport, while it is quantitatively sensitive to specific model assumptions and implementation details. Given its performance and numerical stability, the model can be used to explore bubble behaviors across a broad parameter space relevant to therapeutic ultrasound.

Comments
1

This paper digs into details of bubble dynamics. Cavitation is considered an important mechanism of stone fragmentation. However, bubble dynamics under in vivo conditions is a complex phenomenon and poorly understood. Fluid properties of water and body fluids such as blood or urine vary and result in different dynamic behaviour. The paper focuses on dynamics of single bubbles. Conclusions for a complex interaction of multiple bubbles during SWL are not drawn.

This paper digs into details of bubble dynamics. Cavitation is considered an important mechanism of stone fragmentation. However, bubble dynamics under in vivo conditions is a complex phenomenon and poorly understood. Fluid properties of water and body fluids such as blood or urine vary and result in different dynamic behaviour. The paper focuses on dynamics of single bubbles. Conclusions for a complex interaction of multiple bubbles during SWL are not drawn.
Othmar Wess